Centrifugal drier



Oct. l, 1968 "A, MERCIER v 3,403,785

CENTRIYUCAL DRIER Original Filed May 17, 1966 AGENT Unted States PatentO 3,403,785 Y CENTRIFUGAL DRIER Andr Mercier, La Madeleine, Nord,France, asslgnor to Societe Fives Lille-Cail, Paris, France Continuationof application Ser. No. 550,703, May 12, 1966. This application Oct. 19,1967, Ser. No. 676,658 Claims priority, application France, May 18,1965, 17,397 7 Claims. (Cl. 210-178) ABSTRACT F THE DISCLOSURE Theconical basket of a centrifugal drier is equipped with a supply tube forthe material to be formed whose outlet opening is axially centered andspaced from the closed bottom end of the basket. A guide member partlyprojects coaxially from the outlet opening toward the basket bottom andis covered with a liquid film during drier operation so that viscousmaterial discharged from the supply tube is precisely guided toward thecenter of the basket bottom while separated from the guide member by theliquid film which prevents sticking.

This case is a continuation of my prior copending application Ser. No.550,703, tiled May 17, 1966, and now abandoned.

The present invention relates to centrifugal driers.

In particular, the present invention relates to centrifugal driers whichare adapted to operate continuously and which are particularly intendedto dry a product which is suspended in a liquid. Thus, a continuouslyoperating centrifugal drier of this type will separate the liquid fromthe product suspended therein so that the dried product can then becollected in a condition separated from the initial mother liquor.

Although centrifugal driers of this general type are well known,particular problems are encountered when the product which is to bedried is suspended in a highly viscous fluid. It is accordingly aprimary object of the present invention to provide a centrifugal drierwhich is capable of very effectively handling materials of this type sothat, even if the product which is to be dried is suspended in a highlyviscous mass, it will nevertheless be capable of being eiciently driedwith the structure of the present invention.

Conventional centrifugal driers which operate continuously are providedwith rotary drying baskets which taper downwardly so that they are ingeneral of a frustoconical configuration having a relatively large opentop end and a relatively small closed bottom end which is fixed to oneend of a vertical rotary drive shaft. The material which is to be driedis generally supplied to the interior of the rotary drying basketthrough the open top thereof by way of a suitably calibrated nozzle atthe end of a supply tube and situated in a position coaxial with theaxis of rotation of the drying basket. With this conventionalconstruction, the product which is to be dried simply falls by gravityto the bottom of the basket where the material is then set into rotarymovement as a result of frictional engagement between the material andthe rotating basket. As a result of the centrifugal force which acts onthe material, this material spreads in the form of a thin layer alongthe frustoconical inner surface of the rotary basket, this frustoconicalinner surface forming the inner limiting surface of a perforated wall ofthe basket which forms a sieve or strainer of any type through which theliquid can pass while the product initially suspended in the liquid isretained by this perforated basket wall. The actual drying takes placeas a result of the centrifugal force acting on the material at theperforated side wall of the rotary basket. Thus, the liquid portion ofthe initially introduced 3,403,785 Patented Oct. l, 1968 ICC materialfilters through the sieve formed by the frustoconical side wall of therotary basket, and the product retained by this side wall continues toslide upwardly along the latter, slipping along the inner surface of thesieve until this product is finally ejected at an upper portion of thebasket.

As has been indicated above, driers of this general type cannot be usedin those cases where the viscosity of the mother liquor is too great. Inthe case where the materials introduced into the drier are in a highlyviscous form, these materials are in fact in an intermediate statebetween the liquid and the solid states. As a result, the material has afar greater than negligible resistance to shear and tension. Therefore,when material with these characteristics falls to the bottom end of thebasket of the drier, the stream of this material does not distributeitself uniformly over the bottom of the drier but is instead entrained,without becoming dissociated, toward the periphery of the drier basket.The material then slides upwardly along the inner surface of the basketand is finally ejected from the top end of the basket in the form of asausage-shaped mass without having been dried.

Thus, it is one of the objects of the present invention to provide acentrifugal drier which is particularly suited for efficiently dryinghighly viscous materials under conditions of the type referred to above.

In particular, it is an object of the present invention to provide aconstruction which will reliably direct the material which is to bedried along the axis of rotation of the drying basket so that thematerial will reach the central portion of the bottom of the basket tobe distributed outwardly from this central portion of the bottom of thebasket.

Furthermore, it is an object of the present invention to provide aconstruction which will reduce the extent of viscosity of materialswhich initially are highly viscous, So that in this way it becomeseasier to dry the materials.

In addition, it is an object of the present invention to provide astructure which can accomplish these results in a drier which operatescontinuously.

Also, it is an object of the present invention to provide a constructionof the above type which is simple and rugged and which lends itself toincorporation into existing driers. Of course, the structure of thepresent invention also can be incorporated into new driers.

In accordance with the present invention, there is arranged along theaxis of rotation of the drier basket, at least partly in the interiorthereof, an elongated guide member which extends downwardly along theinterior of the basket to the region of the bottom end thereof. Thesupply means which is provided for supplying the material to be dried tothe interior of the basket through the open top end thereof directs thismaterial for flowing movement downwardly along the exterior surface ofthe guide member. A means is provided for maintaining on this exteriorsurface of the elongated guide member a film of liquid which thusbecomes situated between the guide member and thev material to be driedso as to prevent sticking of the material to be dried onto the elongatedguide member and so as to promote the efficient downward flowing of thismaterial toward the interior bottom end of the drier basket preciselyalong the axis of rotation thereof.

Thus, the material which is to be dried cannot depart from the axis ofthe rotary drier basket and it becomes uniformly `distributed in alldirections along the bottom of the basket. This distribution is enhancedby the fact that the elongated guide member around which the material issituated as it ows toward the bottom of the 'basket forms the materialinto a tubular stream so that the bottom end of the stream which reachesthe bottom end of the basket is of an annular, ring-shaped configurationgreatly enhancing the uniform outward distribution of the material alongthe bottom of the basket.

With the construction of the the invention, moreover, there is theadvantage of bringing about dilution of the liquid phase of the materialto be dried just prior to actual drying, in a manner similar to that setforth in French Patent No. 1,316,550. Thus, the film of liquid on theexterior surface of the elongated guide member can be a liquid solventwhich reaches the bottom of the rotary drying basket together with thematerial to be dried so as to mix intimately with the material to bedried, thus diluting the liquid phase thereof, so as to facilitate thedrying action.

The invention is illustrated by way of example in the accompanyingdrawing which forms part of this application and in which one embodimentof a construction according to the present invention is illustrated, byway of example, in a schematic sectional elevation taken in a planewhich includes the axis of rotation of the drier.

The centrifugal drier shown in the drawing includes a rotory dryingbasket 1 which is of a generally frustoconical configuration and whichhas a closed bottom end fixed to the top end of a rotary drive shaft 2,which rotates at high speed. This drive shaft is supported for rotarymovement by bearings carried by a supporting structure 3 which is inturn mounted on vibration damping elements 4.

The rotary drying basket 1 is situated in the interior of a housingwhich provides around the exterior of the basket 1, below the top endthereof, a chamber C in which the liquid phase of the materialintroduced into the drier is collected after this liquid phase hasbecome separated from the product suspended initially in the liquid.Thus, the drier 1, as shown schematically in the drawing, includes aninner rotary perforated wall 19 forming a sieve and having smallopenings through which the liquid can flow, this inner wall beingsupported by an outer wall structure having larger openings andsupporting the sieve 19. Communicating with the open top end of therotary basket 1 is an outer chamber D of the drier housing, and it is inthis chamber D that the dried products are collected after being ejectedfrom the upper portion of the rotary drier basket 1.

This rotary drier basket 1 has, in the region of its botton end, innerand outer wall portions which are spaced from each other to define theannular space 18 which extends not only along the bottom of the drierbasket but also part of the way upwardly along the side wall thereof.For this purpose the basket 1 has, in its lower interior portion, a bowl14 forming the inner wall and having a lower cylindrical portion whichis joined with an upper perforated frustocoriical portion 1S. Theperforations of the frustoconical portion 15 of the inner wall 14 aregreat enough to permit passage of the largest particles suspended in theliquid of the material to be dried. Suitable spaced studs are xed to theouter bottom wall portion of the rotary basket and support the bowl 14in spaced relation thereto, these studs being situated along the lowerwall portions of the inner wall 14 and the outer wall 16 at the bottomend portion of the rotary basket 1. In this way, the outer wall 16 ofthe basket defines with the inner wall 14 thereof the annular space 18which communicates with the lower horizontal space between the walls 14and 16 and which extends upwardly between the perforated wall portion 15and the sieve 19 to the space which surrounds the upper lip of the innerwall 14 just above the perforated portion 15 thereof. This constructionis analogous to that disclosed in French Patent No. 1,383,840.

The material which is to be dried is supplied to the interior of therotary basket 1 through the open top end thereof by way of a supplymeans which includes a tube 5 communicating with an insulated controlvalve 6 and, when the valve 6 is opened, the material which is to bedried is directed downwardly through the supply means toward theinterior of the bowl or inner wall 14 at the lower central portion ofthe basket 1. The outlet of the valve 6 communicates with an upper openend of an elongated supply tube 7 of the supply means, this tube 7having an axis coincident with the axis of rotation of the basket 1.Tube 7 terminates at its bottom end in a suitably calibrated outletopening 13 forming an outlet nozzle through which the materialdischarges downwardly toward the bottom end of the basket 1. l

In accordance with the present invention, there is situated along theaxis of rotation of the rotary basket 1- an elongated guide member 8which has its own axis coinciding with the axis of rotation of thebasket 1 as well as with the axis of the supply tube 7. This guidemember 8 extends downwardly to the region of the bottom end of thebasket 1. In fact, as is indicated in the drawing, the guide member 8terminates at its bottom end just above the bottom Wall of the innerbowl 14. ln the illustrated embodiment, the elongated guide member 8 isof a hollow tubular construction so that it can receive in its interioran elongated inner tube 9 through which a suitable heating medium isdirected in a manner described below. As is apparent from the drawing,adjacent its upper end the guide member or tube 8 is connected with andsupported by a horizontally and laterally extending tube which extendsto an opening in the tube 7, this latter opening being closed by thislateral tube which communicates with the interior of the tube 8 andthrough which the tube 9 is directed into the interior of thetube 8, inthe manner shown schematically in the drawing.

The tube 9 extends through a central opening' formed in the bottom wallof the bowl 125, and, as is indicated in the drawing, the tube 9 hasconsiderable clearance while passing through this central opening whichotherwise is completely empty. In other words, there are no sealingstructures situated at the bottom wall of the bowl 14 surrounding thetube 9. Thus, by passing through the central opening in the bottom wallof the bowl 14, the tube 9 terminates at its bottom end in a dischargeopening 17 through which it communicates with the space 18 which isdefined between the outer wall 16 and the inner wall 14 of the space 18.

A means is provided for maintaining a film of liquid at the exteriorsurface of the guide member 8 in accordance with the present invention,and this means includes, in the illustrated embodiment, a tubular feedmember 10 which surrounds and is fixed to the tube 8 within the supplytube 7, this tubular member 10 having a closed top end and having -atits bottom end a calibrated annular orifice 11 coaxially surrounding thetubular guide member S so that, through this orifice 11, a film ofliquid will issue to flow downwardly along the exterior surface of theguide member 8. The interior of the tubular member 10 communicatesthrough a conduit 12 with a suitable source of liquid from which theliquid film is formed.

During operation of the apparatus, the material to be dried, such as,for example, massecuite in a sugar refinery, is directed toward theinner bottom portion of the basket 1, into the interior of the bowl 14through the open bottom end 13 of the supply tube 7 of the supply means.Simultaneously, a suitabie solvent is introduced from the conduit 12into the interior of the tube 10 surrounding the elongated guide member8. In the case of massecuite in ya sugar refinery, this solventciansimply be water. The solvent will dilute the liquid phase of thematerial which is to be dried. This solvent flows out of the calibratedoriice 11 at the bottom end of the tubular member 10 and flows along theexterior surface of the guide member 8 in the form of a liquid filmwhich surrounds the guide member 8 and which separates the product whichis to be dried from the exterior surface of the guide member S, so thatin this way the downward flowing of the viscous material is enhanced.The tubular guide member 8 guides the stream of material which is to bedried until it reaches the region of the bottomend of the bowl 14, andthe guide member 8 will maintain the stream of material coaxial with thedrier axis. In this way, a uniform spreading or distribution of thematerial along the -bottom of the bowl 14 is assured.

The solvent which forms the film flowing along the exterior surface ofthe guide member 8 and the material which is to 'be dried are set intorotary movement in the interior of the bowl 14, and the mixture in thebowl 14 of the solvent and the material to be dried results in anextremely rapid dilution of the liquid phase of the material.

As a result of the centrifugal force which acts on the material to bedried, this material in diluted form is advanced upwardly toward theperforated wall portion 15 of the bowl 14. The material, in the dilutedcondition achieved by way of the liquid film, will pass through theopenings of the wall portion 15, these openings being large enough topermit passage of the largest particles, as pointed out above. Thecentrifugal force which thus directs the material through the openingsof the wall portion 15 provides by way of these openings a division ofthe material to Ibe dried. In this way, the material is divided to afine degree and passes outwardly beyond the perforated wall portion 15in the form of relatively fine filament-ary streams or in the form ofdroplets yso that, in this way, the divided material has an extremelylarge outer surface area exposed to the heating fluid which isintroduced by way of the tube 9. This heating fluid discharges from thebottom outlet end 17 of the tube 9 to flow along the space 18 upwardlytherethrough into engagement with the finely divided material whichreaches the space 18 through the openings of perforated wall 15. Theheating fiuid which is introduced through lthe tube 9 will generally bea vaporized form of the solvent which is used for the liquid lm flowingdownwardly along the exterior `surface of the guide member 8. When thissolvent in vaporized form contacts the droplets or filamentary streamsissuing from the openings of the wall portion 15, the vapor condensesand heats the finely divided m-aterial.

The liquid film which flows along the exterior surface of the tube 8together with the material to be dried form a liquid seal at the bottomend of the bowl 14 just above the central lbottom openin-g thereofthrough which the tube 9 extends so that, as a result of this liquidseal, no sealing structure need be provided passage around the tube 9lwhere it passes through the central opening at the bottom wall of thebowl 14.

The material which is to be dried, in diluted and heated condition as aresult of the above-discussed factors, rises upwardly along the sieve 19which forms part of the frustoconical side wall of the rotary basket 1,and the liquid phase of this material will now filter through the sieve19 to be collected in the chamber C. The solid phase continues .to slideupwardly along the sieve 19 and is evacuated at the upper portion of therotary basket 1 to be received in the chamber D.

It is clear that many modifications of the above-described structure canbe provided, by using suitable mechanical equivalents, without departingfrom the invention. The structure of the invention can of course be usedwith a conventional centrifugal drier of known type which operatescontinuously, so that a special structure for reheating the product justbefore the drying thereof is not required.

What is claimed is:

1. In a centrifugal drier, in combination:

(a) a drying basket having an upright axis of rotation and defining acavity about said axis, a portion of said basket closing the bottom ofsaid cavity;

(b) supply means communicating with said cavity for supplying a materialto be dried, said supply means including (1) a supply tube having anoutlet opening in said cavity spaced opposite and axially directedtoward said portion for discharging said material, and

(2) a guide member having a portion projecting from said outlet opening,said portion of the guide member being elongated in an axial directionfrom said outlet toward a free end portion thereof adjacent said portionof the basket,

(3) said projecting portion having a surface exexposed in said cavityfrom said outlet to said free end portion thereof;

(c) means for maintaining a film of liquid on said surface in directcontact with the discharged material and for thereby separating saidmaterial from the guide member lby the contiguously interposed film ofsaid liquid.

2. In a drier as set forth in claim 1, said guide member having anotherportion received in said supply tube.

3. In a drier as set forth in claim 1, said means for maintaining a filmof liquid including a source of said liquid, a tubular feed membersurrounding said other portion of said guide member, said feed membercommunicating with said source and defining with said guide member anannular gap for discharge of said film into said cavity.

4. In a drier as set forth in claim 3, said cavity flaring conicallyfrom said bottom, said basket, said supply tube and said feed memberbeing coaxial, and said opening being directed toward said portion ofsaid basket.

5. In a drier as set forth in claim 1, wall means in said basketadjacent said bottom dividing a space of annular cross-section aboutsaid axis from the remainder of said cavity, said space being upwardlyopen toward said remainder and said Wall means being formed with acentral opening adjacent said axis and connecting said space to saidremainder, and a tube for heatingfiuid axially projecting from saidguide member into said central opening and having a discharge openingcommunicating with said space.

6. In a drier as set forth in claim S, said wall means and said tube forheating fiuid jointly defining an open annular passage connecting saidspace to said remainder, said passage being adapted to be sealed by theliquid of said film.

7. In a drier as set forth in claim 5, a portion of said wall meansspaced from said central opening -being formed with radial perforationstherethrough.

References Cited UNITED STATES PATENTS 2,165,807 7/1939 Murphree et al210-71 X 2,411,660 11/1946 Manning 2102-216 X 2,883,054 4/1959 Sanchez210-377 X 3,207,627 9/ 1965 Dietzel el al 210-71 X 3,226,257 12/ 1965Steele et al. 210-369 X 3,238,063 3/1966 Steele 210-369 X FOREIGNPATENTS 1,316,550 12/ 1962 France. 1,383,840 11/ 1964 France.

14,0131 1892 Great Britain. 832,672 4/ 1960 Great Britain.

REUBEN FRIEDMAN, Primary Examiner.

J. L. DE CESARE, Assistant Examiner.

